Surely...
...having two sensors is as bad as just one?
If one fails, how does the system determine which one it was?
I've mentioned this before, but my diving rebreather has three O2 sensors*.
Part of the pre-dive sequence is to calibrate the unit for the mixes of gases in use. During this calibration, you also watch the mV of the sensors to ensure that they're close to one another.
If one behaves oddly, during the dive, you still have two.
I'll admit I don't have anything to do with safety systems, but to my simple mind, if you're having two sensors surely you either need a way to determine which one is actually at fault, or stick to just one? Or three.
*It never fails to boggle my mind the number of posts online about "I've found a cheaper O2 sensor that seems to work" or "I use a different kind of CO2 scrubber that isn't actually rated to go in rebreathers and none of the major manufacturers have ever tested on but it's cheaper so I'll use it".
Biting the hand that feeds IT
